The prospect of noninvasive mapping of electrical properties of tissues and materials has long been contemplated by scientists. A robust determination of a spatial distribution of electrical conductivity and permittivity can facilitate a wide range of applications in a similarly wide range of fields, from clinical diagnostics to materials science.
Modern imaging modalities have provided a wealth of information about the structure and function of body tissues, both in health and in disease. However, despite the broad array of contrast mechanisms available and the abundance of scientific and diagnostic imaging applications, the underlying electrical properties of tissues in their intact in vivo state have remained largely invisible. Magnetoencephalography or electrocardiography techniques can track an intrinsic electrical activity in the brain or the heart, albeit at coarse spatial resolution. Nonetheless, tissues can be electromagnetic entities, with varying abilities to carry currents and store charges. The ability of heterogeneous tissues to respond to externally applied electromagnetic fields can dictate the success of therapeutic interventions such as transcranial magnetic stimulation or radiofrequency ablation; interactions of electromagnetic fields with the body can distort images obtained with high-field magnetic resonance imaging (MRI) scanners, limiting the practical use of these powerful devices; and invasive measurements have demonstrated that the electrical properties of tumors, for example, can differ dramatically from those of healthy tissue. Indeed, in the field of biomedical imaging, noninvasive electrical property mapping would provide a new tool for the detection and characterization of tumors, while at the same time, a detailed knowledge of electrical properties in vivo would enable both correction of distortions and accurate monitoring and control of patient-specific local energy deposition in high-field MRI. The concept of a “comprehensive electromagnetic superscanner” combining MRI and electrical property mapping has recently been described.
A variety of techniques for the electrical property imaging (or, equivalently, impedance imaging) have been previously described, but each such prior technique has its own notable limitations which have so far prevented widespread use. These techniques may be classified according to two complementary criteria: a) use of injected currents versus applied fields, and b) reliance upon surface measurements versus interior data. Electrical Impedance Tomography (EIT) represents the canonical surface-based technique using injected currents. Alternative surface-based techniques which avoid direct application of currents include Magnetic Induction Tomography (MIT), noise tomography, and Radiofrequency Impedance Mapping (RFIM). All such electrical prospection techniques require the solution of ill-posed inverse problems, which carry with them fundamental challenges of robustness, spatial resolution, etc. Once it was recognized that MRI may be used as a probe of the internal distribution of currents and magnetic fields, however, new techniques for impedance mapping began to emerge, including the injected-current-based MREIT approach, and the field-based electrical property tomography (EPT) technique. These techniques can circumvent the fundamental limitations of surface-based inverse problems, but they contend with the fact that MRI generally provides only partial information about interior currents and fields.
Thus, there remains a need for noninvasive mapping apparatus, systems and computer-accessible medium of the electrical properties of materials that can expand the capabilities of nondestructive testing. Such apparatus, systems and computer-accessible mediums can have potential applications in manufacturing, geology, archaeology, forensics, diagnostics, etc.